Offshore oil and gas platforms have tremendous energy needs. For instance, the electrical loads on fixed and floating offshore facilities are typically supplied by fossil fuel-driven power generating equipment (e.g., diesel generators). Smaller loads, less than about 50 kW, are often supplied by small-scale renewable energy generators such as solar panels or micro-wind turbines. In addition, water desalination for human use, steam production to support oil and gas processing, hydrogen production, and assistance in treatment of exhaust or effluent contaminants typically uses large amounts of energy for removing salt and other minerals from saline water offshore.
Further, pumping applications, such as pumping of water into reservoirs, also require energy, and are commonly electrically driven as a result of fossil fuel combustion at the platform. However, the loads associated with these scenarios can be a large proportion of overall platform energy demand, and are not always critical bus loads. For instance, in some cases, a reservoir can lose pumping pressure for a week or more before economic harm ensues. Generally, pumping water requires the transport of fuel to a platform, combustion to generate power at about 25% to 35% busbar efficiency, and transmission of the power to the load, with inherent line loss and transformer loss. In addition, exhaust emissions and ancillary clean-up expenses such as reagent replenishment to a selective catalytic converter are associated with conventional pumping systems.
A variety of technologies have been investigated to capture energy from ocean waves for use offshore. One example is a point absorber, which is a floating structure with components that move relative to each other due to wave action (e.g. a floating buoy inside a fixed cylinder). Conventional point absorber power take-off (PTO) designs rely on hydraulic rams which pressurize accumulators for driving servomotors to convert mechanical energy into electricity. Other approaches seek to employ permanent magnet generators or linear induction generators for this purpose, but these applications are still at an early stage. However, hydraulic PTO designs may not be an optimal solution for point absorbers in some circumstances. Further, neither the hydraulic ram nor linear generator approach can enable direct drive of desalinization units or water pumping units.
Therefore, a need exists for an alternative to linear generators as a replacement for hydraulic ram PTO designs to capture energy from ocean waves.
In one aspect, embodiments disclosed herein relate to a system for producing an output from wave energy for use on an offshore, nearshore or onshore facility, the system comprising a support structure having a columnar volume with a first opening and a second opening and a movable piston plate housed therein, and a buoyant system surrounding the support structure, wherein the buoyant system is coupled to the piston plate by a linkage system, wherein the piston plate shifts in response to an oscillation of water level causing the buoyant system to shift, wherein air flow within the columnar volume varies in response to the oscillation of water level, and wherein such oscillation is realized at a prescribed rate controlled by a variable tuning orifice.
In other aspects, embodiments disclosed herein relate to a method for producing an output from wave energy for use on an offshore, nearshore or onshore facility, the method comprising the steps of incorporating a structural support having a columnar volume into said offshore, nearshore or onshore facility, wherein the structural support comprises a movable piston plate therein, wherein the structural support is surrounded by buoyant system that oscillates, wherein the piston plate is coupled to the buoyant system with a linkage system, wherein the buoyant system, linkage system, and piston plate move in response to wave energy, and wherein air enters a first opening and leaves from a second opening formed in a structural support of the facility in response to movement of the piston plate and incorporating a variable tuning orifice within the columnar volume of the support structure to finely regulate oscillation of the system.
It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, are merely intended to conceptually illustrate the structures and procedures described herein. Reference numerals may be repeated among the figures in order to indicate corresponding or analogous elements.